Parallelogram Side Length: Finding Missing Side Given 20cm and 60cm Perimeter

Question

A parallelogram has a perimeter of 60 cm.

AB = 20 cm

Calculate the length of the other side.

00:00 Find AC

00:03 Opposite sides are equal in parallelograms

00:17 They are also a pair of opposite sides therefore equal

00:26 The perimeter of the parallelogram equals the sum of its sides

00:37 Let's substitute appropriate values and solve for BD

00:57 Let's group the numbers into one factor, and BD

01:07 Let's isolate BD

01:22 This is the length of BD

01:29 And this is the solution to the question

To solve this problem, we'll use the perimeter formula for a parallelogram, which is:

$P = 2(a + b)$

where $P$ is the perimeter, $a$ is the length of one side, and $b$ is the length of the adjacent side.

Given:

Let's apply these values to the formula:

$60 = 2(20 + b)$

To isolate $b$ , we first divide both sides by 2:

$30 = 20 + b$

Now, solve for $b$ by subtracting 20 from both sides:

$b = 10 \, \text{cm}$

Therefore, the length of the other side is 10 cm.